The present invention relates to a radio communication apparatus, having combined functions as a terminal adapter, a digital radio communication apparatus, a facsimile communication apparatus and so on, for being connected to a digital public communication line.
Lately, as the ISDN (Integrated Services Digital Network) is widely adopted, a data terminal such as a personal computer or the like is connected to ISDN via a terminal adapter for data communication.
In this case, the data terminal (hereinafter referred to as PC) is connected to the terminal adapter by a cable, e.g., RS232C, and transmits data to the terminal adapter according to an asynchronous scheme at the transmission speed of, e.g., 2400 bps, 4800 bps, 9600 bps, 19.2 Kbps, 38.4 Kbps and so forth. The terminal adapter converts the transmission speed of the received data to 64 Kbps according to the CCITT (International Telegraph and Telephone Consultative Committee) Standard Recommendation V. 110, I. 460, and transmits the converted data to ISDN.
Since the terminal adapter is connected to ISDN which serves as a public communication network, other media such as the telephone, facsimile and the like which are used to communicate audio data or image data, are generally connected to an analogue port of the terminal adapter.
FIG. 17 is a block diagram showing a system construction using a conventional terminal adapter.
Referring to FIG. 17, reference numeral 2101 denotes a terminal adapter; 2102, a PHS (Personal Handyphone System) master unit connected to a first analogue port of the terminal adapter; 2103, a PHS slave unit; 2104, a personal computer (PC) connected to the terminal adapter by RS232C cable; 2105, a scanner connected to the PC by a cable; 2106, a printer connected to the PC by a cable; 2107, a facsimile apparatus connected to the second analogue port of the terminal adapter; and 2108, ISDN.
FIG. 18 is a block diagram showing an internal structure of the conventional terminal adapter.
Referring to FIG. 18, reference numeral 2201 denotes a CPU (microcomputer); 2202, a memory; 2203, a data bus; 2204, an ISDN interface unit including DSU (Digital Service Unit); 2205, a B-channel serial signal; 2206, an HDLC (High-level Data Link Controller) which assembles/disassembles data frames transmitted through ISDN; 2207, an RS232C interface unit; and 2208, an analogue port to which a terminal connectable to an analogue public communication line is connected.
FIGS. 19 and 20 show communication sequences when data is transmitted/received via a conventional terminal adapter.
Steps of performing data communication using a conventional terminal adapter are now described.
First, when data communication is performed by using PC 2104, a communication command (e.g. AT command transmitted between a communication unit and a data terminal) outputted by the PC 2104, is received by the serial communication interface unit 2207. The serial communication interface unit 2207 outputs an interruption request to the CPU 2201, and in the interruption processing executed in response to the interruption request, the serial communication interface unit 2207 notifies the CPU 2201 that the data has been received. The CPU 2201 transfers the received data transmitted by the PC 2104 via the serial communication interface 2207 to the memory 2202. When the CPU 2201 analyzes the AT command sent by the PC 2104 and recognizes that the transmission is addressed to ISDN, the CPU 2201 starts-up the ISDN interface unit 2204 to perform transmission processing. Upon receiving a response message from ISDN, the AT command is transmitted to the PC 2104 via the serial communication interface unit 2207, and notifies the PC 2104 that the called party has responded.
Then, the PC 2104 starts data transmission through the terminal adapter. The data subjected to transmission is stored in the memory 2202 similar to the AT command. Next, the CPU 2201 writes the data stored in the memory into the HDLC controller 2206. The data is assembled into an HDLC frame format by the HDLC controller 2206, and is transmitted by the CPU 2201 to ISDN.
Conversely, data reception from ISDN is detected by the HDLC controller 2206 and stored in the memory 2202. The CPU 2201 writes the stored data into the serial communication controller 2207 and outputs it to the PC 2104 through the RS232C cable.
Meanwhile, the PHS master unit 2102, facsimile apparatus 2107 and the like can be connected to the analogue port of the terminal adapter 2101. If the PHS master unit 2102, which has received a transmission request from the PHS slave unit 2103, performs transmission processing (inversion), the CPU 2201 detects the transmission request via the analogue port 2208 of the terminal adapter 2101, and performs transmission processing to ISDN. Accordingly, communication using PHS is realized. The same description applies to a facsimile apparatus.
However, the above-described terminal adapter is connected to a PC only by a cable, e.g., the RS232C cable. Therefore, the PC must be placed near the terminal adapter. If the PC is set far from the connection portion of the public communication line, a long cable is necessary, requiring wiring works.
Further, since the public communication line is shared by the telephone unit, facsimile apparatus and terminal adapter and further the PC is connected to the terminal adapter, printer and scanner, line connections are complicated and require a large set-up area.
Furthermore, in the conventional system, each of the resources (devices), e.g., the PHS system connected to the terminal adapter 2101, scanner 2105 connected to the PC 2104, printer 2106, facsimile apparatus 2107 and so on, cannot efficiently be used in the entire system, result being wasteful, where similar functions are separately provided by plural devices.
The present invention is made in consideration of the above situation, and has as its object to improve a radio communication apparatus.
Another object of the present invention is to provide a communication system where a PC can be connected to a public communication line, even in a case where the PC is not connected to a terminal adapter by a cable, by utilizing the digital radio communication technology which is widely used recently.
Moreover, another object of the present invention is to provide a terminal adapter including functions for a printer, scanner, facsimile and telephone to be controlled integrally, so as to improve operability, save space and reduce cost.
Furthermore, another object of the present invention is to adopt a structure using multiple CPUs and a shared register, which enable to add the functions of terminal adapter and PHS master unit to the conventional facsimile apparatus without requiring large changes, so as to realize a highly-expandable radio communication apparatus.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.